[Haskell-cafe] Span function

[R J]

Can someone provide a hand calculation of:
    span (< 0) [-1, -2, -3, 0, 1, 2, -3, -4, -5]?
I know the result is ([-1, -2, -3], [0, 1, 2, -3, -4, -5]), but the recursion flummoxes me.
Here's the Prelude definition:
    mySpan                     :: (a -> Bool) -> [a] -> ([a], [a])    mySpan _ []                =  ([], [])    mySpan p xs@(x:xs')        | p x                  =  (x:ys, zs)        | otherwise            =  ([], xs)                               where                                   (ys, zs) = mySpan p xs'
Thanks.
 		 	   		  
_________________________________________________________________
Hotmail has tools for the New Busy. Search, chat and e-mail from your inbox.
http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_1
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.haskell.org/pipermail/haskell-cafe/attachments/20100607/ea7268e2/attachment.html